This invention relates to new polycyclic phthalazine derivatives, particularly 2-carboxyalkyl- and 2-carboxyaryl-substituted maduraphthalazines (10,12,15,16-tetrahydroxy-8-methoxy-11-methyl-1,9,14-trioxo-1,2,6,7,9,14-h exahydronaphthaceno-[1,2-g]-phthalazines) as well is salts, esters and amides thereof. They constitute substances which exhibit a strong antibacterial effect against Staphylococci, particularly against gram-positive Staphylococci, and especially against multi-resistant Staphylococci (MRSA) and resistant Enterococci, and can be used for combatting infectious diseases in humans and animals. These compounds are suitable for the production of very different pharmaceutical preparations and forms of application.
The compounds are the first representatives of a hitherto unknown ring system, namely of naphthaceno-[1,2-g]-phthalazine. They are derived from madurahydroxylactone or maduranic acid, which can be obtained by a biotechnology route from Actinomadura rubra (W. Fleck, D. G. Strauss, J. Meyer, Z. Allg. Mikrobiol. 18, 368-398 (1978)). The structure of madurahydroxylactone (formula II) has been elucidated by Paulus and co-workers (E. F. Paulus, K. Dornberger, W. Werner, D. Fenske, Acta Cryst. (1994) C50, 2064-2067). Madurahydroxylactone itself only exhibits an unsatisfactory biological efficacy. Madurahydroxylactone forms part of the benzonaphthacenequinone class, from which benanomycins and pradimycins in particular have recently become known as antifungal substances of interest (T. Oki in "Recent Progress in Antifungal Chemotherapy", Eds. H. Yamaguchi, G. S. Kobayachi, H. Takahashi, Marcel Dekker, Inc., New York, Basle, Hong Kong, 1992, page 38).